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pair_traits for getting pair types without instantiating.

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I was having some problems in an abandoned prototype with incomplete
types, I'm not sure I will have this problem now, but I'm keeping this
anyway, as it seems useful.
This commit is contained in:
Daniel James
2017-02-23 20:14:27 +00:00
parent 81aefde94e
commit 79cf0c4bfb
2 changed files with 22 additions and 4 deletions
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22
include/boost/unordered/detail/implementation.hpp
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@ -337,6 +337,23 @@ struct compressed
compressed& operator=(compressed const&);
};
////////////////////////////////////////////////////////////////////////////
// pair_traits
//
// Used to get the types from a pair without instantiating it.
template <typename Pair> struct pair_traits
{
typedef typename Pair::first_type first_type;
typedef typename Pair::second_type second_type;
};
template <typename T1, typename T2> struct pair_traits<std::pair<T1, T2> >
{
typedef T1 first_type;
typedef T2 second_type;
};
#if defined(BOOST_MSVC)
#pragma warning(push)
#pragma warning(disable : 4512) // assignment operator could not be generated.
@ -3186,10 +3203,11 @@ template <class ValueType> struct set_extractor
#endif
};
template <class Key, class ValueType> struct map_extractor
template <class ValueType> struct map_extractor
{
typedef ValueType value_type;
typedef typename boost::remove_const<Key>::type key_type;
typedef typename boost::remove_const<typename boost::unordered::detail::
pair_traits<ValueType>::first_type>::type key_type;
static key_type const& extract(value_type const& v) { return v.first; }

4
include/boost/unordered/detail/map.hpp
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@ -29,7 +29,7 @@ template <typename A, typename K, typename M, typename H, typename P> struct map
typedef typename pick::link_pointer link_pointer;
typedef boost::unordered::detail::table_impl<types> table;
typedef boost::unordered::detail::map_extractor<K, value_type> extractor;
typedef boost::unordered::detail::map_extractor<value_type> extractor;
typedef typename boost::unordered::detail::pick_policy<K>::type policy;
@ -62,7 +62,7 @@ struct multimap
typedef typename pick::link_pointer link_pointer;
typedef boost::unordered::detail::grouped_table_impl<types> table;
typedef boost::unordered::detail::map_extractor<K, value_type> extractor;
typedef boost::unordered::detail::map_extractor<value_type> extractor;
typedef typename boost::unordered::detail::pick_policy<K>::type policy;